Wireless communication links are well known and widely used in connection with backhaul communication. Here, the expression “backhaul communication” is used for the communication between a core network or similar (e.g. such as the
Evolved Packet Core (EPC) in the Long Term Evolution (LTE)) and one or several radio access nodes or similar (e.g. one or several base stations or similar) in a wireless communication network, and/or the communication that occurs between one or several radio access nodes and an access node controller or similar (e.g. a Base Station Controller (BSC) or a Radio Network Controller (RNC)) in a wireless communication network, and/or between an access node controller and the core network or similar.
A typical wireless communication link is schematically illustrated in FIG. 1. It is preferred that the link 110 is a Line of Sight (LOS) wireless communication link. It is also preferred that the link 110 is fixed, i.e. the emitting and receiving parts of the link 110 are preferably fixed and aligned with respect to each other and can therefore not be operationally moved or transported from one position to another. Typically, LOS links use highly directional antennas arranged such that the antenna lobe of a first antenna (e.g. Tx1) points at a second antenna (e.g. Rx2) and such the antenna lobe of the second antenna (e.g. Tx2) points at the first antenna (e.g. Rx1). Reflections or similar are typically avoided and/or suppressed with respect to known fixed LOS links, e.g. due to the narrow antenna lobes used in this connection.
As can be seen in FIG. 1 the known link 110 comprises a first node N1 with a first antenna Tx1 and a second node N2 with a second antenna Rx1. The nodes N1, N2 and the antennas Tx1, Rx1 respectively are arranged to operatively communicate information via a wireless transmission path 110. The nodes N1, N2 and the antennas Tx1, Rx2 may be arranged to communicate information via the transmission path 110 in one direction only (unidirectional), or in both directions, Tx1/Rx1=Tx2/Rx2 (bidirectional), not shown in FIG. 1. The information may e.g. communicated via the transmission path 110 by means of a microwave signal, e.g. utilizing microwaves above 1 GHz, or above 6 GHz or above 30 GHz, or above 50 GHz including various forms of light.
A drawback associated with the known link 110 is that a malfunction in either node N1, N2 may cause a complete shutdown of the link. Generally, this is not acceptable in commercial applications. For example, microwave links that are used for backhaul communication in wireless mobile communication systems are required to function substantially without any downtime. This means that wireless links for backhaul communication should be more robust against hardware and software failures than link 110.
FIG. 2 shows a known 1+1 wireless communication link arrangement 200 that is more robust to hardware and software failures. The link arrangement 200 comprises a primary uni-directional link 210 as described above with reference to FIG. 1 and an additional secondary wireless uni-directional link 220. It is preferred that the secondary link 220 is substantially identical to the primary link 210. Both links 210, 220 are typically a part of the first and second node N1, N2 respectively. Thus, the first node N1 may have a first antenna with transmitter Tx1 and a second antenna transmitter Tx2, whereas the second node N2 may have a first antenna with receiver Rx1 and a second antenna receiver Rx2. In the link 210 the nodes N1, N2 and the antennas of Tx1 and Rx1 are arranged so as to operatively communicate information via a primary wireless transmission path 210, whereas the nodes N1, N2 and the antennas of Tx2, Rx2 are arranged to operatively communicate information via a secondary wireless backup transmission path 220. The secondary transmission path 220 may be identical or substantially identical to the primary transmission path 210. In normal operation the link arrangement 200 uses the primary link 210 as shown in FIG. 2A. In case of a malfunction at either node N1 or N2 affecting the communication via the primary link 210 the link arrangement 200 can continue the operation by switching the communication to the secondary link 220 as shown in FIG. 2B. Thus a malfunction will rarely cause a shutdown of the whole link arrangement 200.
A drawback associated with the known link arrangement 200 is that the secondary link 220 increases the cost of the link arrangement 200 while remaining substantially idle as a redundant backup resource most of the time. For effective communication, one has to install or configure as many numbers of transmitters and receivers on both the transmission and reception side, which again leads to complexity at the individual nodes, further leads to installation cost and maintenance.
Considering that a backhaul link should generally be operational close to 100% of the time. This requirement is emphasized as the demand on backhaul wireless communication links rises, e.g. due to the more effective base stations in the Long Term Evolution (LTE) defined within the framework of the 3rd Generation Partnership Project requiring backhaul communication with Gigabit capacity or more between the radio access node(s) (i.e. a base station such as the NodeB or the eNodeB) and a core network and/or a core network node.
Thus, there seems to be a need for a wireless communication link arrangement that provides an increased capacity, low cost, low maintenance, less complex particularly in case of a failure.